Guo Shoujing

Guo Shoujing (Chinese: 郭守敬; pinyin: Guō Shǒujìng; Wade–Giles: Kuo Shou-ching, 1231–1316), courtesy name Ruosi (若思), was a Chinese astronomer, engineer, and mathematician born in Xingtai, Hebei and lived during the Yuan Dynasty (1271–1368). The later Johann Adam Schall von Bell (1591–1666) was so impressed with the preserved astronomical instruments of Guo that he called him "the Tycho Brahe of China."

Early life

In 1231, in Xingtai, Hebei province, China, Guo Shoujing was born into a family which soon had to let him go. The names of his parents are unknown, as Guo's father died while he was a child and his mother left him to be raised primarily by his paternal grandfather, Guo Yong. His grandfather was famous throughout China for his expertise in a wide variety of topics, ranging from the study of the Five Classics to astronomy, mathematics, and hydraulics. Guo was raised learning everything his grandfather presented to him, soon propelling him to a new level of mastery of the engineering world. He became curious as a child, playing with objects, figuring out what the world was about and how he could change it or make it better. He became somewhat of a prodigy, showing exceptional promise. By the age of 14 or 15, he obtained a blueprint for a water clock which his grandfather was working on, and realized its principles of operation. He improved the design of a type of water clock called a lotus clepsydra, which is a water clock that has a bowl shaped like a lotus flower on the top into which the water dripped. After he had mastered the construction of such water clocks, he began to study mathematics in a rigorous fashion at the age of 16. From mathematics, he began to understand, more complexly, the science of hydraulics, as well as the study of astronomy. This foundation of learning set up the stage for the rest of his life and his contributions to society.

Later life

At the same time as Guo Shoujing began to reach out into the world and apply his mathematical genius to society, Genghis Khan died and his son, Ogodei, began to conquer south into China. Guo, at the age of 20, became a hydraulic engineer, working close to his home city to improve the municipal water supply. In 1251, working as a government official, he helped to repair a bridge over the Dahuoquan River. His hydraulic expertise did not go unnoticed. In the late 1250s, Kublai Khan became the official Khan and ruler of most of China, which had been conquered by the Mongols and was still under their control. Zhang Wenqian, a friend of Guo’s and a government official, informed Kublai Khan himself that Guo was the leading hydraulics expert of the time. Kublai Khan realized the importance of hydraulic engineering, irrigation, and water transport, which he believed could help alleviate uprisings within the empire. Kublai sent Guo to look at these aspects in the area between Dadu (now Beijing or Peking) and the Yellow River. To provide Dadu with a new supply of water, Guo found the Baifu spring in the Shenshan Mountain and had a 30 km channel built to bring the water to Dadu. He proposed connecting the water supply across different river basins, built new canals with many sluices to control the water level, and achieved great success with the improvements which he was able to make. The Grand Canal, which had linked the river systems of the Yangtze, the Huai, and the Huang since the early 7th century, was repaired and extended to Dadu in 1292–93 with the use of corvée (unpaid labor). After the success of this project, Kublai Khan was overwhelmingly pleased and sent him off to manage similar projects in other parts of the empire. He became the chief advisor of hydraulics, mathematics, and astronomy for Kublai Khan.

During this time, Guo also began to construct astronomical instruments. The most important instruments he invented were the gnomon, the square table, the abridged or simplified armilla, and a water powered armillary sphere called the Ling Long Yi. The gnomon is used to measure the angle of the sun, determine the seasons, and is the basis of the sundial, but Guo Shoujing revised this device to become much more accurate and improved the ability to tell time almost precisely. The square table was used to measure the azimuth of celestial bodies by the equal altitude method and could also be used as protractor. The abridged or simplified armilla was used to measure the angle of the sun, topography, the direction of north, as well as the position of any celestial body. The Ling Long Yi is similar to an abridged armilla except larger, more complex, and more accurate. Kublai Khan, after observing Guo’s mastery of astronomy, ordered that he, Zhang, and Wang Xun set out to make a more accurate calendar. The first thing they did was design a new observatory near Dengfong. After construction was complete, they built 26 other observatories throughout China in order to gain thorough observations for their calculations. In 1280, Guo completed the calendar, calculating a year to be 365.2425 days, just 26 seconds off the year calculated currently. This calendar was used for hundreds of years in China, leading them to have the most accurate calendar in the world, closely followed by the Gregorian calendar. In 1283, Guo was promoted to director of the Observatory in Beijing and, in 1292; he became the head of the Water Works Bureau. Throughout his life he also did extensive work with spherical trigonometry. After Kublai Khan’s death, Guo continued to be an advisor to Kublai’s successors, working on hydraulics and astronomy.

Death

Little is known of the death of Guo Shoujing. The only information found about his death is that he died in 1316 in China. It can be deduced that he died of old age or an illness related to old age. He was most likely working on mathematics, astronomy, and hydraulics long into his old age, making more discoveries and innovations to add to his repertoire. It is safe to say he most likely never left China his entire life, working the whole time within the country in order to make it better or make new discoveries. He died at the age of 85 and probably held a very high, noble standing in society at the time of his death.

Analysis of his contributions

Guo Shoujing changed everything in Chinese science at the time relating to astronomy, hydraulics, or mathematics. The tools he invented for astronomy allowed him to calculate the near exact time of the year; 301 years before the Gregorian calendar. This allowed the Chinese culture to set up a whole new system of exact dates and times, allowing for increasingly accurate recording of history and a sense of continuity throughout the country. The calendar stabilized the Chinese culture through continuity and, consequently, dynasties were able to rule with a degree more stability. It was a tool of societal stability, even though it was simply intended to create a more accurate calendar. Through his work in astronomy, he was also able to more accurately establish the location of celestial bodies and the angles of the Sun relative to Earth. He invented a tool which could be used as an astrological compass, helping people find north using the stars instead of magnets.

Within the field of hydraulics, even at a young age, Guo was revolutionizing old inventions. His work on clocks, irrigation, reservoirs, and equilibrium stations within other machines allowed for a more rewarding and effective result. For clocks and equilibrium components, he made them more accurate and precise allowing for better results. If a machine was not in equilibrium and needed to be to function, it would end up with the wrong answer or result, thus making the machine useless. He made sure that astronomical and mathematical machines used to read angles, weights, and position all were fitted with equilibrium systems stemming from his work in hydraulics. The watches he perfected through his work in hydraulics allowed for an extremely accurate reading of the time. For irrigation, he provided the correct hydraulics systems in order for water to be distributed equally and for transport to be swift and effective. His irrigation plans changed communities so that they could establish effective trading and the community could prosper. In the category of reservoirs, his most memorable engineering feat is the man-made Kunming Lake in Beijing. This enormous lake provided water for all of the surrounding area of Beijing and allowed for the best grain transport system in the country. His work with other such reservoirs allowed people in inner China access to water for planting, drinking, and trading. All of his work in hydraulics allowed communities throughout China to flourish and China moved forward as an economic power. Guo’s work in mathematics was regarded as the most highly knowledgeable mathematics in China for 400 years. Guo worked on spherical trigonometry, using a system of approximation to find arc lengths and angles. He stated that pi was equal to 3, leading to a complex sequence of equations which came up with an answer more accurate than the answer that would have resulted if he did the same sequence of equations, but instead having pi equal to 3.1415.

Past historical interpretations

For several hundred years after Guo Shoujing made his major discoveries and did his revolutionary work in various fields, he was still regarded as the best Chinese astronomer, mathematician, and engineer. But, as people began to add onto his work, the authenticity of his work was questioned. Some believe that he took Middle Eastern mathematical and theoretical ideas and used them as his own, taking all the credit. It might have been true that he had similar ideas and waves of thinking, but it is highly unlikely that he stole ideas from others. The biggest point against this is that he never left China and thus could not have had access to their ideas. He also had more complex ideas than anyone else of the time so even if he had stolen ideas, he would have had to have added onto them, making them new and original. It is unclear whether this is true or not, but the facts state otherwise. Otherwise, Guo was highly regarded throughout history, by many cultures, as a precursor of the Gregorian calendar as well as the man who perfected irrigation techniques in the new millennium. Many historians regard him as the most prominent Chinese astronomer, engineer, and mathematician of all time. He began the pull of China into the future. He also presented China with its first glimpse of being an economic power through his hydraulic work. Overall, historians believe him to be one of the most prominent figures, in any field, in Chinese history.

Contributions

He worked on improving the Chinese gnomon and worked at Kublai Khan's Gaocheng Astronomical Observatory. He set up 27 observation centers in different parts of China. There he formulated the Shoushili calendar (授時曆) in 1281 and calculated the year to be 365.2425 days, only 26 seconds off the real time; this is the same as the Gregorian calendar, but 301 years earlier. This calendar would be used for the next 363 years, the longest period during which a calendar would be used in Chinese history. He also used mathematical functions in his work relating to spherical trigonometry, building upon the knowledge of Shen Kuo's (1031–1095) earlier work in trigonometry. It is debated amongst scholars whether or not his work in trigonometry was based entirely on the work of Shen, or whether it was partially influenced by Islamic mathematics which was largely accepted at Kublai's court. Sal Restivo asserts that Guo Shoujing's work in trigonometry was directly influenced by Shen's work. An important work in trigonometry in China would not be printed again until the collaborative efforts of Xu Guangqi and his Italian Jesuit associate Matteo Ricci in 1607, during the late Ming Dynasty.

He devised a number of astronomical instruments, and conducted large-scale geodetic surveys and celestial observations. Although he did a great deal of work on the modern calendar, he suggested a value of 3 for pi, as opposed to Zu Chongzhi's 3.14159265 and Zhang Heng's 3.142.

In engineering he is best known for constructing the artificial Kunming Lake in Beijing as a reservoir and part of a new waterway for grain transport.

Asteroid 2012 Guo Shou-Jing is named after him.

References

• Asiapac Editorial. (2004). Origins of Chinese Science and Technology. Translated by Yang Liping and Y.N. Han. Singapore: Asiapac Books Pte. Ltd. ISBN 981-229-376-0.
• Engelfriet, Peter M. (1998). Euclid in China: The Genesis of the First Translation of Euclid's Elements in 1607 & Its Reception Up to 1723. Leiden: Koninklijke Brill. ISBN 90-04-10944-7.
• Ho, Peng Yoke. (2000). Li, Qi, and Shu: An Introduction to Science and Civilization in China. Mineola: Dover Publications. ISBN 0-486-41445-0.
• Needham, Joseph (1986). Science and Civilization in China: Volume 3, Mathematics and the Sciences of the Heavens and the Earth. Taipei: Caves Books, Ltd.
• Restivo, Sal. (1992). Mathematics in Society and History: Sociological Inquiries. Dordrecht: Kluwer Academic Publishers. ISBN 1-4020-0039-1.
• O'Connor, J. J., and E. F. Robertson. "Guo Shoujing." School of Mathematics and Statistics. Dec. 2003. University of St. Andrews, Scotland. 7 Dec. 2008 <http://www-history.mcs.st-andrews.ac.uk/Biographies/Guo_Shoujing.html>.
• "China." Encyclopædia Britannica. 2008. Encyclopædia Britannica Online School Edition. 24 Nov. 2008 <http://school.eb.com/eb/article-71727>.
• Kleeman, Terry, and Tracy Barrett, eds. The Ancient Chinese World. New York, NY: Oxford UP, Incorporated, 2005.
• Shea, Marilyn. "Guo Shoujing - 郭守敬." China Experience. May 2007. University of Maine at Farmington. 15 Nov. 2008 <http://hua.umf.maine.edu/China/astronomy/tianpage/0018Guo_Shoujing6603w.html>.
• "China." Encyclopædia Britannica. 2008. Encyclopædia Britannica Online School Edition. 24 Nov. 2008 <http://school.eb.com/eb/article-71735>.

External links

• O'Connor, John J.; Robertson, Edmund F., "Guo Shoujing", MacTutor History of Mathematics Archive, University of St Andrews
• Article on the Shoushi calendar from the National University of Singapore
• Culture story site
• Guo Shoujing at the University of Maine